Consider Use of Changeable Message Signs in Improving Driver Comprehension of Work Zone Zipper Merge Operations.

Driving Simulator Study and Survey Used to Assess Driver Response to Work Zone Merge with Varying Types and Placement of Signs.

Date Posted

Optimizing Work Zone Zipper Merge Using Federated Driving Simulators

Summary Information

A common concern for state departments of transportation (DOTs) as an area of safety risk is the “taper,” the area before a work zone lane closure where the merge takes place. Researchers in Missouri conducted a driving simulator study with 50 participants to explore the influence of Changeable Message Signs (CMSs) on driver behavior in a work zone zipper merge. The study included assessing educational content provided on zipper merge and CMS location (300 or 700 feet from taper) under varying speed (40 or 55 miles per hour) and flow conditions in the simulator as well as a participant survey. Using an eye tracker system, researchers assessed when drivers looked at signs including a CMS directing a zipper merge (a “MERGE HERE” sign) and driver merge behavior. Simulator data at first use of lane change signal, at merge, and at the taper were analyzed to compare speed, distance to taper, and distance between the merging vehicle and the next vehicle in the destination lane.

Lessons Learned

  • Implement changeable message signs as opposed to static signs to enhance comprehension of messages to drivers. Seventy-two percent of the respondents stated that they preferred the CMS over the static sign. When CMS messages “MERGE AHEAD” and “USE BOTH LANES” were compared with similar static signs, more respondents stated that they did not understand the sign with static signs (22 percent) as compared to the CMS (2 percent).
  • Enhance public education as it is vital to achieving understanding of zipper merge and intended behavior. Prior to educating the participants, 60 percent of them stated they were not familiar with the zipper merge. The results from the simulator study showed a statistically significant difference in driver behavior between participants who were provided educational content before and after the simulator drive.  After being educated on the zipper merge, participants merged closer to the taper (a desired behavior for zipper merge), and 94 percent of them considered the message helpful. Participants who were provided zipper merge information in advance also merged later when the CMS was located closer to the taper.
  • Avoid lengthy public education materials. With both the simulator and the survey, a short, concise message explaining zipper merge were found effective to educate the participants. The researchers also recommended using video over written educational materials, although survey results show that both proved to be effective.
  • Take driver perceptions into account when selecting effective zipper merge scenarios. The literature, simulator results, and survey responses sometimes provided different recommendations for traffic flow and speeds where zipper merge could be effective. Over 30 percent of survey respondents said a work zone zipper merge could cause anxiety.

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